Neonatal Abstinence Syndrome (NAS) refers to a range of clinical symptoms experienced by a baby after birth following withdrawal from a physically addictive substance.1 This occurs when a foetus is chronically exposed to an addictive substance in the womb. These substances may be illicit, prescribed, opioids or non-opioids.2 Research has indicated that around 1% of babies born in the UK are exposed to physically addictive drugs in utero,2 though incidence rates can vary significantly depending on regional drug use.
What causes NAS
NAS occurs when a foetus is chronically exposed to a physically addictive substance taken by the mother during pregnancy. Physically addictive substances can be both illicit and prescribed. The most common cause of NAS is opioid use, which includes both synthetic opioids like methadone and fentanyl, and natural opiates such as heroin, codeine, and morphine.2 These substances readily cross the placenta, affecting the foetus just as they would an adult, leading to physical dependence. When the baby is born, opioid stimulation stops abruptly, and the baby experiences withdrawal symptoms.
Low-dosage, short-term use of less potent opioids such as codeine and morphine may be prescribed during pregnancy if there is a clinical need for the drug which meets particular criteria. Still, the NHS advises against long-term use of opioids at this time to lower the risk of NAS.3
Although the long-term use of both prescribed and illicit opioids during pregnancy is the most common cause of NAS, there are several non-opioid drugs which can also cause NAS-like symptoms when used during pregnancy. Prescribed antidepressants such as selective serotonin reuptake inhibitors (SSRIs) and anti-anxiety medications such as benzodiazepines are also physically addictive drugs which can be passed to the baby during pregnancy and cause NAS-like symptoms at birth.2 The risks associated with different antidepressants vary, so it is essential to consult a healthcare professional when making decisions about their use during pregnancy.
Symptoms of NAS
NAS symptoms can vary between cases however the common symptoms include:2
- Increased muscle tone
- Tremor
- Seizures
- Agitation
- Myoclonic jerks (involuntary twitching/jerking)
- Diarrhoea
- Vomiting
- Difficulty gaining weight
- Bradycardia (slow heart rate)
- Dehydration
- Aponea
- Nasal flaring
- Excessive sucking
As mentioned above, symptoms can vary between cases, however, it is reported that polysubstance abuse – the use of more than one addictive substance – is associated with worsened NAS symptoms of the baby and a higher risk of pregnancy abnormalities and sudden infant death syndrome (SIDS).2 Polysubstance abuse during pregnancy also increases the risk of overdose in the mothers.4 A national survey study in the US found that around one in nine pregnant women reported current alcohol use, with 40% of these women also using other substances like tobacco and marijuana.5
Diagnosis
When doctors suspect that a baby has NAS, doctors typically ask the mother about her substance use during pregnancy. The topic's sensitivity can make diagnosis challenging, as some individuals may not wish to disclose this information out of fear of judgment or involvement of social services. If the mother has a known history of substance abuse this may not be necessary.
Doctors may also take a urine sample from the infant for toxicology testing, although these tests must be conducted within a limited time frame before the drugs are metabolised.2 Toxicology testing may also be conducted on tissue samples from the umbilical cord.6 If the baby has CNS dysfunction symptoms (particularly common after NAS caused by cocaine or opioid use during pregnancy), doctors may wish to conduct MRI or cranial ultrasounds to check for structural damage of the brain.2
The symptoms of NAS are scored by trained healthcare professionals using the adapted ‘Finnegan Neonatal Abstinence Scoring System’.8 Doctors use this standardised scoring system to monitor changes in symptoms multiple times a day.7 High scores indicate a clinically significant severity of withdrawal which may require pharmacological treatment. This monitoring continues until the infant consistently scores below a certain threshold for at least a few days.
Treatment
Treatment of NAS depends on the severity of symptoms and the specific substance used. Treatment can last days, weeks or even longer depending on the severity of withdrawal symptoms.
Most cases of NAS are due to opioid exposure before birth; in these cases, up to 75% of infants need pharmacological intervention for their withdrawal from opioids.7 This can include giving the infant morphine, methadone or buprenorphine to try to alleviate the severity of symptoms to lessen distress and promote healthy functions such as feeding and sleeping.9 The infant is then slowly weaned off the drug after symptoms stabilise. While naloxone is used to reverse opioid overdoses in adults, it is not used in infants due to the risk of seizures.
In addition to pharmacological treatment, supportive care is an additional focus of treatment.7 Supportive care focuses on providing an environment that reduces distress for the infant. This includes providing a quiet, dark environment and feeding based on demand.
Attempts are made where possible to involve the mother of an infant with NAS in its treatment and monitoring, so that they are aware of symptoms related to NAS at home, and continue to provide a low-stimulation environment if the baby experiences distress after discharge.
Breastfeeding and NAS:
Breastfeeding is generally encouraged for mothers of infants with NAS, as it can reduce the severity of symptoms and reduce the amount of time that the infant needs drug treatment and hospitalisation.10
In some circumstances, there may be risks associated with breastfeeding that outweigh the above benefits. If the mother is a chronic alcohol user, or is not engaged in a treatment programme for substance abuse, healthcare professionals are likely to discourage breastfeeding to avoid re-exposure of addictive substances to the infant.10 Additionally, there have been several reported cases of NAS following abrupt cessation of breastfeeding if the mother has been using opioids – even when the infant was not born with NAS.10
Substance abuse is associated with a higher risk of contracting bloodborne diseases – e.g. hepatitis B, hepatitis C and HIV.7,10 Hence, if the mother is confirmed positive with one of these diseases, they will be advised against breastfeeding to prevent transmission of the disease to the infant.
Foetal alcohol spectrum disorder (FASD) vs. NAS: what’s the difference?
Foetal Alcohol Spectrum Disorder (FASD) describes a group of disorders lasting throughout a child’s life and into adulthood which arise from alcohol exposure in the womb.11 On the other hand, NAS refers to the immediate symptoms of withdrawal observed after birth when a foetus has developed a physical addiction to a substance as a result of its mother using drugs during pregnancy, most commonly opioids. The incidence of FASD is not well-established, as its symptoms and severity can vary, and diagnosis methods may be different between healthcare providers. FASD can cause various physical, developmental, and cognitive impairments, including abnormal organ function, reduced growth, intellectual disabilities, and sensory abnormalities.11
Summary
To conclude, Neonatal Abstinence Syndrome (NAS) is a condition characterized by withdrawal symptoms in newborns exposed to addictive substances before birth. Symptoms and severity of NAS differ between cases, as different substances give rise to different symptom profiles. Opioids are the most common drug to cause NAS, which often requires the use of pharmacological interventions to treat. Supportive care is another treatment which is almost always given in cases of NAS, either in isolation or in combination with pharmacological treatment. This includes creating a low-stimulation environment for the infant to reduce distress.
References
- Anbalagan S, Mendez MD. Neonatal Abstinence Syndrome. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 May 9]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK551498/.
- Kurup U, Merchant N. Neonatal abstinence syndrome: management and current concepts. Paediatrics and Child Health [Internet]. 2021 [cited 2024 May 9]; 31(1):24–31. Available from: https://www.sciencedirect.com/science/article/pii/S1751722220301773.#
- Pregnancy, breastfeeding and fertility while taking codeine. nhs.uk [Internet]. 2022 [cited 2024 May 9]. Available from: https://www.nhs.uk/medicines/codeine/pregnancy-breastfeeding-and-fertility-while-taking-codeine/.
- CDC. Polysubstance Use During Pregnancy. Centers for Disease Control and Prevention [Internet]. 2023 [cited 2024 May 9]. Available from: https://www.cdc.gov/pregnancy/polysubstance-use-in-pregnancy.html.
- England LJ. Alcohol Use and Co-Use of Other Substances Among Pregnant Females Aged 12–44 Years — United States, 2015–2018. MMWR Morb Mortal Wkly Rep [Internet]. 2020 [cited 2024 May 9]; 69. Available from: https://www.cdc.gov/mmwr/volumes/69/wr/mm6931a1.htm
- Wexner Medical Center. Umbilical Cord Tissue Toxicology Testing [Internet]. Ohio State University ; [date unknown]. Available from: https://medicine.osu.edu/-/media/files/wexnermedical/healthcare-professionals/clinical-labs/test-catalog/umbilical-cord-toxicology-testing.pdf?la=en&hash=984F1F2864DE0DD6A44B31FAFBF22480D075A19E#:~:text=The%20analysis%20of%20drugs%20in,newborn%20urine%20and%20maternal%20urine.
- [Internet]. Neonatal Abstinence Syndrome (NAS) – NCPOEP; [cited 2024 May 9]. Available from: https://ncpoep.org/guidance-document/neonatal-abstinence-syndrome-overview/neonatal-abstinence-syndrome-nas/.
- Finnegan LP, Connaughton JF, Kron RE, Emich JP. Neonatal abstinence syndrome: assessment and management. Addict Dis. 1975; 2(1–2):141–58.
- Mangat A, Schmölzer G, Kraft W. Pharmacological and Non-pharmacological treatments for the Neonatal Abstinence Syndrome (NAS). Semin Fetal Neonatal Med [Internet]. 2019 [cited 2024 May 9]; 24(2):133–41. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451887/.
- Holmes AP, Schmidlin HN, Kurzum EN. Breastfeeding Considerations for Mothers of Infants with Neonatal Abstinence Syndrome. Pharmacotherapy [Internet]. 2017 [cited 2024 May 9]; 37(7):861–9. Available from: https://accpjournals.onlinelibrary.wiley.com/doi/10.1002/phar.1944.
- CDC. Basics about FASDs. Centers for Disease Control and Prevention [Internet]. 2023 [cited 2024 May 9]. Available from: https://www.cdc.gov/ncbddd/fasd/facts.html.